In medical terminology, a geode is another term for which bone lesion?

• A. A subchondral cyst
• B. A bone spur
• C. A cortical fracture line
• D. A soft tissue edema

Answer: (A)

A geode is a subchondral cyst—a fluid-filled cavity in the subarticular bone just beneath the joint cartilage, most commonly seen with osteoarthritis. It forms when synovial fluid from the joint penetrates fissures in the cartilage and enters the subchondral bone, creating a cystic area that often has a sclerotic rim on imaging. This makes it different from a bone spur (an osteophyte at the joint margin), a cortical fracture line (a fracture through the bone cortex), or soft tissue edema (fluid in the surrounding soft tissues). So the geode corresponds to a subchondral cyst.